1) can expenses of replacing a bathtub for a walk-in-shower for prevention of fall be deducted as medical expenses?

Yes.  If your doctor prescribed the jacuzzi for the treatment of a medical condition, then you can deduct some or all of the cost of the jacuzzi as a medical expense.  However, the amount you deduct will be the amount of the jacuzzi minus the increased in value of your house.  So, if you paid $10,000 for the Jacuzzi and it caused your home value to increase by $6,000, you would only be able to claim $4,000 as an itemized expense.

For the walk in shower the same applies.  It must be needed due to a medical condition in order to be tax deductible as an itemized expense.

Keep in mind, your home modifications and all medical expenses are only deductible for the amount that is over 7.5% of your AGI.  This means if your AGI is $50,000, then the amount that is over $3,750 is deductible.  

Itemized expenses include mortgage interest, gambling losses up to winnings,  charitable contributions, state and local taxes up to $10,000, medical expenses in excess of 7.5% of your AGI and casualty and losses in excess of 10% of you AGI with the first $100 not counting towards the loss.  

Then your total itemized expenses would need to be greater than your standard deduction below in order to benefit from your expenses. 

The 2024 Standard Deductions are as follows:

• Married Filing Joint (MFJ)              $29,200
• Married Filing Separate (MFS)      $14,600
• Head of Household (HOH)             $21,900 
• Single                                                 $14,600                                

Blind or over 65 and MFJ or MFS add $1,550

Single or HOH if blind or over 65 add $1,950

Standard versus Itemized Deduction

Possibly.

First, you would need a letter of medical necessity from your doctor, in case you are audited.

Second, you can only include the cost if it does not increase the value of your home.  Improvements that increase the value of your home are adjustments to cost basis, and may reduce your capital gains when you sell, but are not deductible medical expenses even if they are medically necessary.   Whether or not an improvement increases the value of your home is something you may need to discuss with a real estate professional.   The IRS has a list of improvements that it considers do not increase the value of the home and would be deductible (see below), but a bathroom remodel is not on that list, so you may need to discuss with a professional.  (As the population ages, certain accessibility improvements may increase the value of the home especially in certain neighborhoods.)

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"Certain improvements made to accommodate a home to your disabled condition, or that of your spouse or your dependents who live with you, don't usually increase the value of the home and the cost can be included in full as medical expenses. These improvements include, but aren't limited to, the following items.

"Only reasonable costs to accommodate a home to your disabled condition are considered medical care. Additional costs for personal motives, such as for architectural or aesthetic reasons, aren't medical expenses."